Harris County burns down last 6 of Arkema's chemical...

1of11Smoke is visible coming from the Arkema Inc. plant Sunday, September 3, 2017, in Crosby. A spokeswoman for the Harris County Fire Marshal's office said Sunday afternoon that the Arkema Inc. plant is igniting the remaining six containers of chemicals at its Crosby plant.

10of11Frances Breaux tears up while talking to media about her close friends and neighbors Leo and Lajayne Opelia, both in their 70s. She hasn't being able to reach them since last night, before the organic peroxides inside the Arkema chemical plant exploded Thursday, Aug. 31, 2017, in Crosby, Texas. The Opelias were mandatorily evacuated from their homes by officials but they decided to sneak back in their home. ( Godofredo A. Vasquez / Houston Chronicle )Photo: Godofredo A. Vasquez, Arkem_Harvey2017

11of11Frances Breaux tears up as she looked for photos of her close friends and neighbors Leo and Lajayne Opelia, both in their 70s, to show members of the media. She hasn't being able to reach them since last night, before the organic peroxides inside the Arkema chemical plant exploded Thursday, Aug. 31, 2017, in Crosby, Texas. The Opelias were mandatorily evacuated from their homes by officials but they decided to sneak back in their home. ( Godofredo A. Vasquez / Houston Chronicle )Photo: Godofredo A. Vasquez, Harvey2017

Spokeswoman Rachel Moreno refused to provide any details about what was done to set the material on fire, citing "safety and security aspects' of the operations.

"We did it in a very safe manner," Moreno said.

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John Rull, who lives in Newport, a nearby neighborhood to the Arkema chemical plant in Crosby, shot this footage of the explosions at the plant on Sunday, September 3.

Video: Houston Chronicle

Crosby residents saw thick pillars of black smoke around the area until about 5 p.m., though Moreno could not confirm if the fire was still burning at that time. A 1.5-mile radius surrounding the plant has been evacuated.

The fire marshal's office called the ignition of the containers "a proactive approach to minimize the impacts to the community."

The public was not told about the change in plans until after operations began. A press release was sent out by both Arkema and the fire marshal's office.

John Rull was sitting on his porch in Newport, mere miles from the evacuation zone, when he heard the two big booms, back to back. Another boom shook the skies about 30 seconds later, he said, and several minutes later, he heard a fourth.

Suddenly, black smoke started to unfurl, covering a wide span of the sky. Half an hour later, the black smoke lingered.

Rull, 30, had been jolted by the explosion on Friday, which he also heard from his home, 2 miles from the Crosby plant. This series was louder and created much more smoke, he said.

"We're just hoping it's all over and done with now," he said, adding that the company gave him no indication that it would combust the materials. "We've been on pins and needles waiting to see if we'd have to leave."

It's not the first time the company and government officials have kept the public in the dark over the situation at Arkema.

This week, the company and the Texas Commission on Environmental Quality both refused to provide a chemical inventory of the plant to the public. While the Environmental Protection Agency did air monitoring at the site, it did not release the data from those monitors. The EPA did say the monitoring showed there were no "toxic concentrations" away from the evacuated zone.

Arekma issued a press release late Sunday afternoon saying destruction efforts started at 5 p.m. but Rull and others say they saw smoke from the site more than hour before that.

Rull, who works as a chemical blender in Seabrook, said that while he understands that companies in many situations keep information on their operations private, he felt nervous as a citizen and wanted Arkema to release more about what materials were in the vans.

"You don't know what's in there. You don't know what's in the air. Their time for keeping secrets is up," Rull said.

Company officials, who said they made the decision to set off the last six containers, said they believe that the chemicals in the trailers have been decomposing. The chemicals, highly volatile organic peroxides that explode and catch fire when temperatures rise, have been decomposing since late Monday night.

Without the vehicles catching flames, however, they would not be able to know if the chemicals are totally neutralized, spokesman Jeff Carr said.

The company needs to be confident that the chemicals are no longer active before it sends in safety officials and air quality observers, Carr said.

"There's quite a lot to do, and nothing's going to happen until the chemicals burn down," Carr said.

The EPA called the operation a "controlled burn" of the material in a statement.

The TCEQ said the decision aimed to prevent "additional damage to the facility or spreading into the surrounding area" in a statement Sunday. First responders are in the area, but outside evacuation radius, that agency said.

Up to this point, agencies were in public agreement that a 1.5 mile evacuation radius was conservative and highly unlikely to need extending.

It is not yet when families will be able to move back into their homes in the evacuation zone. Carr said flooding around the plant had diminished by Sunday afternoon.

"Once the fire has gone out, they'll go in and make sure the air quality is good, the water quality is good and then it'll be a process of letting people know that they can come back in," Moreno said. "But they won't be back until it is 100 percent safe for them to go back."

Arkema said at 6:30 p.m. that the six containers "largely burned themselves out" but that residents should not return home yet.

Two of the company's nine containers caught fire on Friday afternoon, following the first container igniting early Thursday morning. Fires with the volatile chemicals caused plumes of black smoke and towering flames at the plant, which is northeast of Houston.

Initially, the company said it would not destroy or neutralize the chemicals. It also considered moving the chemicals but deemed that process too risky.

The six containers ignited Sunday were "kind of grouped together," Moreno said.

"For us to be in a position where we were going to put that material into trailers and try to move it, it runs the risk of not being able to get it out of the area or getting it stuck in traffic, or having a fire or an explosion at a highway or at a public area, versus in the rural area where this site is," Daryl Roberts, a company safety official, said.